65616821 has 8 divisors (see below), whose sum is σ = 71872920. Its totient is φ = 59627008.

The previous prime is 65616797. The next prime is 65616857. The reversal of 65616821 is 12861656.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 4558225 + 61058596 = 2135^2 + 7814^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 65616821 - 2¹⁸ = 65354677 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65615821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 66056 + ... + 67041.

It is an arithmetic number, because the mean of its divisors is an integer number (8984115).

Almost surely, 2^65616821 is an apocalyptic number.

It is an amenable number.

65616821 is a deficient number, since it is larger than the sum of its proper divisors (6256099).

65616821 is a wasteful number, since it uses less digits than its factorization.

65616821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133143.

The product of its digits is 17280, while the sum is 35.

The square root of 65616821 is about 8100.4210384399. The cubic root of 65616821 is about 403.3404036888.

The spelling of 65616821 in words is "sixty-five million, six hundred sixteen thousand, eight hundred twenty-one".